The present invention relates to electrophoretic displays and electronic apparatuses provided with the electrophoretic displays.
In recent years, portable information apparatuses have rapidly developed. Thin displays of low-power consumption are increasingly required. A variety of developments are attempted to meet these requirements. Liquid crystal displays have satisfied such requirements.
The liquid crystal displays, however, still have unresolved problems, such as unsatisfactory visibility due to a viewing angle to the screen and reflected light and visual load due to a flickering light source. Thus, displays having reduced visual load have been intensively researched.
Reflective displays are promising in view of low-power consumption and reduced load to eyes. One of the displays is an electrophoretic display as disclosed in U.S. Pat. No. 3,612,758.
The principle of operation of the electrophoretic display is shown in FIG. 2. The electrophoretic display comprises charged particles 11, a dispersion of an insulating colored fluid 12 containing a dissolved dye, and a pair of substrates 15 and 15 opposing each other and holding the dispersion.
Each of the pair of substrates 15 and 15 is provided with a transparent electrode 14, and a voltage applied through the transparent electrode 14 moves the charged particles 11, which are charged electrophoretic particles, toward the electrode having the opposite polarity. Displaying is achieved by the contrast of the color of the charged particles 11 (electrophoretic particles) to the color of the colored fluid 12. The shape of the electrode can be appropriately changed to perform desired displaying.
For example, in a case of white charged particles 11 and a non-white colored fluid 12, the white charged particles 11 (electrophoretic particles) are attracted to an electrode at a viewer side under a voltage having a polarity, and the viewer sees a white display having a desired shape on the back of the color of the colored fluid 12. In contrast, the charged particles 11 (electrophoretic particles) are attracted toward the opposite electrode under a voltage having the opposite polarity and the viewer sees the color of the insulating colored fluid.
This electrophoretic display is made by a method which includes bonding the pair of substrates 15 and 15, each provided with the transparent electrode 14, separated by spacers 13 to form a cell, and loading the dispersion into the cell by a capillary phenomenon. Because sedimentation of the charged particles 11 occurs in this method, the life of the electrophoretic display is short.
A method for making an electrophoretic display is proposed in which microcapsules containing an insulating colored fluid and charged particles dispersed into the colored fluid and a binder are applied onto a substrate by a roll coater or the like.
FIG. 3 is a conceptual view of the resulting electrophoretic display, and FIG. 4 is a conceptual view of the electrophoretic display shown in FIG. 3, viewed from the display section (display face) side. In FIG. 3, reference numeral 31 represents a transparent electrode, reference numeral 32 represents a charged particle, reference numeral 33 represents a colored fluid, reference numeral 41 represents a microcapsule, reference numeral 34 represents a binder, and reference numeral 35 represents a substrate. Also, in this electrophoretic display, the viewer sees the color of the charged particles 32 or the color of the colored fluid 33 from the display section side depending on the polarity from the power source. In this electrophoretic display, the shape of the electrode can also be appropriately changed to perform desired displaying.
Traditional electrophoretic displays using microcapsules, however, have problems such as poor coloring and low contrast because the binder is present between the microcapsules and the substrate to reduce the area in which the substrate at the display face side constituting a substantial display section constituting the display face is in contact with the microcapsules. The binder is also present in the adjacent microcapsules to form portions not contributing to the displaying in the display region, resulting in reduced contrast.